This is purely my opinion and speculation, but I think SG's case and the bodies are all related, and I also think this will end up involving something more than murder, such as trafficking. Somebody posted a link the other day to a forum where a woman claiming to be a local said that JB was in the truck that was looking for SG that night. If that is true, then it seems to be a lot of effort by a most likely selfish john to track down an hysterical prostitute. If his personality is what I suspect it to be, he wouldn't be out looking for her; he would shrug it off. Also, him getting in the car with the driver would put him in a very vulnerable position, especially if they were successful and found her. Now he is outnumbered in the vehicle by a prostitute and a driver. Wealthy and privileged men who normally pay to bring women to them don't put themselves in this situation. In fact, chauvinistic men do far less for women they work with or are related to, let alone women they hired into the most subservient of all roles. If she really became hysterical and caused so much grief that night in his house and neighborhood, I would think it would be more likely for him to react with serious agitation and annoyance, even going so far as to spin it around and call the police himself, portraying himself as the victim. Also, he would lock his door, stay inside and leave the driver to deal with this mess. Who cares what the neighbors think -- frankly, people living in remote and exclusive beachside communities are used to seeing a lot of strange things.
I am also intrigued by the call purporting to be from the doctor. Remember, the SG incident occurred before any bodies were found, so the perpetrator or group of perpetrators might have been willing to take more risks back then. Maybe the call was simply to buy some time -- they might have already had interaction with many victims' families by this point (even beyond what has already been reported), and maybe they know the sorts of stories that easily satisfy curious relatives.
Second, is Overstreet a common last name? I was intrigued when I saw that ALC's real surname is Overstreet, and that she had spent some time recently in Florida. Overstreet is the surname of the cousin that was the focus of much attention in the Cummings case down there. I don't really see any real connection, except the possibility for some sort of remote family connections.